The invention relates to a delivery of a machine for processing flat printing materials, in particular, a sheet-processing rotary printing machine, having a sheet guide surface over which the sheets are drawn during operation, with forcible guidance of an edge of the sheets that extends in a processing direction, respectively, having nozzles which open into the sheet guide surface and through which flow occurs during operation, and having a blown air curtain, formed during operation, which extends over the sheet guide surface transversely to the processing direction and is aimed at a target region on the sheet guide surface; and to a machine for processing flat printing materials, which is equipped with the delivery.
A delivery of the aforementioned type is disclosed, for example, in the published German Patent Document DE 195 24 641 A1. The blown or blast air curtains disclosed therein and outputted by dryers, and the nozzles opening into the sheet guide surface, form a configuration such that the target region of a respective blown air curtain is provided with a row of nozzles, these nozzles producing a flow which is oriented in the processing direction.
This mutual association of nozzles and blown air curtains is used to counteract the effect which otherwise occurs that a corresponding blown air curtain forces the sheet passing the latter in the area of the target region in a direction towards the sheet guide surface as long as the sheet covers the target region.
It is accordingly an object of the invention to provide a delivery of a machine for processing flat printing materials which is of such construction that the risk of having the trailing end of a respective sheet turn up as it leaves the target region is counteracted.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a delivery of a machine for processing flat printing materials, having a sheet guide surface over which the sheets are drawn during operation, with forcible guidance of an edge of the sheets extending in a processing direction, respectively, comprising nozzles opening into the sheet guide surface and providing flow therethrough during operation, and a blown air curtain, formed during operation, which extends over the sheet guide surface transversely with respect to the processing direction and is aimed at a target region on the sheet guide surface, the nozzles being arranged on the sheet guide surface in accordance with a first mode and a second mode, the nozzles arranged in accordance with a first of the modes outputting during operation a flow which counteracts a volume flow, from the blown air curtain, which is deflected downline with respect to the processing direction.
In accordance with another feature of the invention, the nozzles arranged in accordance with the first mode are located within a strip of the sheet guide surface extending transversely to the processing direction and form a grid the extent of which transverse to the processing direction is matched to the corresponding extent of the maximum format of the sheets which can be processed.
In accordance with a further feature of the invention, the nozzles arranged in accordance with the first mode output blown air jets directed counter to the processing direction.
In accordance with an added feature of the invention, the nozzles arranged in accordance with a second of the modes are subdivided into two groups by an imaginary center line extending in the processing direction and bisecting the sheet guide surface, and the nozzles of a respective one of the two groups output flows during operation which are directed away from the imaginary center line.
In accordance with an additional feature of the invention, the nozzles arranged in accordance with the first and the second mode differ in the distribution thereof on the sheet guide surface, and the nozzles located on a respective side of the imaginary center line output flows during operation which are directed identically to one another.
In accordance with yet another feature of the invention, the nozzles arranged in accordance with the first mode are associated with a blown air supply, which supplies these nozzles independently of the nozzles arranged in accordance with the second mode.
In accordance with a concomitant aspect of the invention, there is provided a machine for processing flat printing materials, having a delivery provided with a sheet guide surface over which sheets are drawn during operation, with forcible guidance of an edge of the sheets extending in a processing direction, respectively, comprising nozzles opening into the sheet guide surface and providing flow therethrough during operation, and a blown air curtain, formed during operation, which extends over the sheet guide surface transversely with respect to the processing direction and is aimed at a target region on the sheet guide surface, the nozzles being arranged on the sheet guide surface in accordance with a first mode and in accordance with a second mode, the nozzles arranged in accordance with a first of the modes outputting during operation a flow which counteracts a volume flow, from the blown air curtain, which is deflected downline with respect to the processing direction.
In order to achieve the aforestated object of the invention, the delivery is configured to the effect that the nozzles are arranged on the sheet guide surface in accordance with a first and a second mode, the nozzles arranged in accordance with a first of the modes outputting during operation a flow which counteracts a volume flow, from the blown air curtain, which is deflected downline with respect to the processing direction.
The target region which is located on the sheet guide surface and at which the blown air curtain is aimed is then acted upon by the latter with blown air, respectively, when a trailing end portion of the respective sheet no longer covers the target region and a leading end portion of a following sheet or a gripper system forwarding the following sheet does not yet cover the target region. During this time interval, given a conventional configuration of the delivery mentioned at the at the introduction hereto, and the equipment of the latter with a blown air curtain in the form of a dryer outputting hot-air doctors, in particular a part of the blown air curtain deflected downline by the sheet guide surface becomes effective so that it blows under the trailing portion of a respective sheet and causes this end portion to turn up. This results in a very detrimental influence on the sheet run, which has multiple effects, inasmuch as it can lead to lubrication problems and to problems when gripping the sheets by a subsequent sheet brake. In order to counter these problems, it was necessary to operate with low dryer outputs, i.e., with a low volume flow and a low flow velocity of the hot-air doctor, but this necessitated a relatively low processing speed in the case of a correspondingly insufficient drying result, and a great deal of effort was necessary in order to set the parameters influencing the air cushion in order to guide the sheets so as to float.
All these problems are eliminated by the invention in a surprisingly simple way in that a blown air curtain output by a dryer is prevented from blowing underneath the trailing end portion of a respective sheet, specifically as a result of the fact that, in the aforementioned target region, a volume flow of the blown air curtain which is deflected downline is counteracted by a flow.
Although the invention is illustrated and described herein as embodied in a delivery of a machine processing flat printing materials, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: